Recently, it has become generally accepted that the non-renewable energy resources of our planet are becoming exhausted. In particular, the term ‘peak oil’ is now commonly used as shorthand to represent the observation that global oil production has already peaked and is now in decline, while the global demand for energy continues to grow. Moreover, scientific and popular debate about the existence and extent of climate change caused by human activities (also referred to as ‘global warming’) has become largely settled, bolstered by unprecedented changes and extremes in both global and local climactic conditions, with often disastrous consequences for humans and other living species, including great loss of life in many instances.
The general acceptance of global warming as a threat to our quality of, life and perhaps even our very existence has greatly intensified the search for renewable energy sources with low or zero emissions of greenhouse gases (often referred to for convenience as ‘low carbon’ or ‘non-carbon-based’ energy resources). Of the many different forms of renewable energy available, many consider that solar energy holds the greatest hope. For example, simple calculations indicate that the solar energy impinging upon even a relatively small area of unoccupied land in Australia is equal to the world's current energy needs, suggesting that photovoltaic energy conversion devices may be the best way to generate electrical power for the foreseeable future whilst minimising further contributions to global warming.
These considerations have given rise to an intense focus on research and development of photovoltaic devices globally. Although photovoltaic devices per se are far from new and have been commercially available for many decades, the major barrier that has prevented their uptake on a large scale has been their substantial cost relative to conventional non-renewable sources of energy, and in particular to fossil fuels such as coal, oil, and gas. Consequently, a major goal of current research efforts in photovoltaics is to produce low cost, high efficiency photovoltaic devices that can generate electrical energy at an overall cost (per Watt) that is equal to or less than the cost of energy produced from non-renewable energy sources, the situation of equal cost being referred to as ‘grid parity’.
To this end, a wide range of new photovoltaic devices are being developed, based on a wide range of materials, including not only elemental and compound semiconductors (predominantly amorphous, multi-crystalline, and micro-crystalline silicon), but also polymers, and photo-sensitive dyes. However, a dominant theme of these efforts is to simplify and refine the manufacturing process as far as possible to minimise the total cost per device, a strategy that has been extremely successful for the US-based company First Solar, Inc., whose business model is now being widely copied by other manufacturers. Thus large-scale, simple manufacturing processes are widely accepted as the solution to the global need for low-cost renewable energy with minimal generation of greenhouse gases.
It is desired to provide an optoelectronic device and an optoelectronic device manufacturing process that alleviate one or more difficulties of the prior art, or that at least provide a useful alternative.